Adaptive EDCF: Enhanced service differentiation for IEEE 802.11 wireless ad-hoc networks

This paper describes an adaptive service differentiation scheme for QoS enhancement in IEEE 802.11 wireless ad-hoc networks. Our approach, called adaptive enhanced distributed coordination function (AEDCF), is derived from the new EDCF introduced in the upcoming IEEE 802.11e standard. Our scheme aims to share the transmission channel efficiently. Relative priorities are provisioned by adjusting the size of the contention window (CW) of each traffic class taking into account both applications requirements and network conditions. We evaluate through simulations the performance of AEDCF and compare it with the EDCF scheme proposed in the 802.11e. Results show that AEDCF outperforms the basic EDCF, especially at high traffic load conditions. Indeed, our scheme increases the medium utilization ratio and reduces for more than 50% the collision rate. While achieving delay differentiation, the overall goodput obtained is up to 25% higher than EDCF. Moreover, the complexity of AEDCF remains similar to the EDCF scheme, enabling the design of cheap implementations

Perbandingan Priority Queueing (PQ) dan Fair Queueing (FQ) pada 802.11e EDCA untuk Meningkatkan Performansi QoS VoIP over WLAN

IEEE 802.11e didesain untuk kebutuhan QoS pada aplikasi realtime seperti VoIP dan Video streaming. Parameter-parameter layer 2 MAC 802.11e EDCA memungkinkan Wireless Router atau Access Point (AP) memprioritaskan pengiriman frame trafik VoIP daripada frame trafik tidak realtime salah satunya FTP. Akibatnya trafik selain VoIP menjadi menderita akibat mekanisme antrian Priority Queueing (PQ) yang terdapat pada 802.11e EDCA. Teknik antrian Fair Queueing (FQ) dengan variannya Core Stateless Fair Queueing (CSFQ) memberikan kesempatan yang sama pada setiap antrian. Paper ini menyajikan perbandingan antara teknik antrian PQ dan CSFQ untuk dibandingkan hasil pengukuran QoS latency, paket hilang, dan throughput dengan beban trafik yang heterogen yaitu trafik VoIP dan FTP. Pengujian dilakukan dengan menggunakan Network Simulator- 2.34 (NS-2.34) dengan hasil latency CSFQ lebih baik daripada PQ dengan nilai 9 ms dan 52 ms untuk 6 pengguna VoIP atau 3 peer komunikasi. Sedangkan untuk paket hilang dan throughput PQ menunjukkan hasil yang lebih baik daripada CSFQ walaupun pengguna VoIP aktif dinaikkan sampai 20 pengguna atau 10 peer komunikasi

A simple and fair proposal to improve the performance of the IEEE 802.11e enhanced coordination function

A simple and fair proposal to improve the performance of the IEEE 802.11e standard is presented in this paper. Our proposal is accomplished by means of increasing the priority of those queues that have not been able to transmit during certain period of time, depending on the elapsed time waiting to transmit. Results show that this proposal improves the performance of wireless networks using IEEE 802.11e EDCF since low priority queues reduce their waiting time to access the channel and high priority queues are not degraded.8th IFIP/IEEE International conference on Mobile and Wireless CommunicationRed de Universidades con Carreras en Informática (RedUNCI

Adaptive Distributed Fair Scheduling for Multiple Channels in Wireless Sensor Networks

A novel adaptive and distributed fair scheduling (ADFS) scheme for wireless sensor networks (WSN) in the presence of multiple channels (MC-ADFS) is developed. The proposed MC-ADFS increases available network capacity and focuses on quality-of-service (QoS) issues. when nodes access a shared channel, the proposed MC-ADFS allocates the channel bandwidth proportionally to the packet\u27s weight which indicates the priority of the packet\u27s flow. The packets are dynamically assigned to channels based on the packet weight and current channel utilization. The dynamic assignment of channels is facilitated by use of receiver-based allocation and alternative routes. Moreover, MC-ADFS allows the dynamic allocation of network resources with little added overhead. Packet weights are initially assigned using user specified QoS criteria, and subsequently updated as a function of delay and queued packets. The back-off interval is also altered using the weight adaptation. The weight update and back-off interval selection ensure global fairness is attained even with variable service rates

Анализ применимости методов обеспечения QoS для повышения производительности мобильной радиосети специального назначения

Классификация и анализ известных методов обеспечения QoS с точки зрения целесообразности их применения для увеличения производительности мобильной радиосети специального назначенияyesБелгородский государственный университе

Throughput Analysis of Primary and Secondary Networks in a Shared IEEE 802.11 System

In this paper, we analyze the coexistence of a primary and a secondary (cognitive) network when both networks use the IEEE 802.11 based distributed coordination function for medium access control. Specifically, we consider the problem of channel capture by a secondary network that uses spectrum sensing to determine the availability of the channel, and its impact on the primary throughput. We integrate the notion of transmission slots in Bianchi's Markov model with the physical time slots, to derive the transmission probability of the secondary network as a function of its scan duration. This is used to obtain analytical expressions for the throughput achievable by the primary and secondary networks. Our analysis considers both saturated and unsaturated networks. By performing a numerical search, the secondary network parameters are selected to maximize its throughput for a given level of protection of the primary network throughput. The theoretical expressions are validated using extensive simulations carried out in the Network Simulator 2. Our results provide critical insights into the performance and robustness of different schemes for medium access by the secondary network. In particular, we find that the channel captures by the secondary network does not significantly impact the primary throughput, and that simply increasing the secondary contention window size is only marginally inferior to silent-period based methods in terms of its throughput performance.Comment: To appear in IEEE Transactions on Wireless Communication

Adaptive Distributed Fair Scheduling and Its Implementation in Wireless Sensor Networks

A novel adaptive and distributed fair scheduling (ADFS) scheme for wireless sensor networks is shown through hardware implementation. In contrast to simulation, hardware evaluation provides valuable feedback to protocol and hardware development process. The proposed protocol focuses on quality-of-service (QoS) issues to address flow prioritization. Thus, when nodes access a shared channel, the proposed ADFS allocates the channel bandwidth proportionally to the weight, or priority, of the packet flows. Moreover, ADFS allows for dynamic allocation of network resources with little added overhead. Weights are initially assigned using user specified QoS criteria. These weights are subsequently updated as a function of delay, enqueued packets, flow arrival rate, and the previous packet weight. The back-off interval is also altered using the weight update equation. The weight update and the back-off interval selection ensure that global fairness is attained even with variable service rates. The algorithm is implemented using UMR/SLU motes for an industrial monitoring application. Results the hardware implementation demonstrates improved performance in terms of fairness index, flow rate, and delay

Route Aware Predictive Congestion Control Protocol for Wireless Sensor Networks

Congestion in wireless sensor networks (WSN) may lead to packet losses or delayed delivery of important information rendering the WSN-based monitoring or control system useless. In this paper a routing-aware predictive congestion control (RPCC) yet decentralized scheme for WSN is presented that uses a combination of a hop by hop congestion control mechanism to maintain desired level of buffer occupancy, and a dynamic routing scheme that works in concert with the congestion control mechanism to forward the packets through less congested nodes. The proposed adaptive approach restricts the incoming traffic thus preventing buffer overflow while maintaining the rate through an adaptive back-off interval selection scheme. In addition, the optimal routing scheme diverts traffic from congested nodes through alternative paths in order to balance the load in the network, alleviating congestion. This load balancing of the routes will even out the congestion level throughout the network thus increasing throughput and reducing end to end delay. Closed-loop stability of the proposed hop-by-hop congestion control is demonstrated by using the Lyapunov-based approach. Simulation results show that the proposed scheme results in reduced end-to-end delays